Thermostatic switch



Feb 16, l954 R. J. D. ROBERTS ETAL THERMOSTATIC SWITCH Feb. 1

Filed June 9, 1952 R J. D. ROBERTS ET AL THERMOSTATIC SWITCH 2 Sheets-Sheet 2 @fau 65 20 fm/eww Patented Feb. 16, 1954 rTHERMOSTATIC 'SWITCH Ray J.. D. .Roberts and Alfred H. Faulkner, Chicago, Ill., assignors to Charles D. Hummel, Sr.,

New York, N. Y.

Application-June 9, 1952, SerialNofZBZAl 17 Claims. 1 4Ou-r invention relates 'to a thermostatic switch and more specifically to -a switch of this type wherein a 'latch is utilized which 'requires 'manual resetting of the switch.

An `object of this invention is to provide improvements in a thermostatic switch in which `a temperature responsive latch is `rutilized to hold the switch in an operating position, :and in which the switch parts move definitely, consistently and suddenly :apart when ka given thermal condition lis reached fas a result of an overload.

As 'another object oi our invention, we have provided a thermostat-ic .switch .in which the thermostatic element and the circuit breaking parts are separate from one another, so that the break in the circuit eirected ylby the switch does 'not occur in any part of the latch structure Aor at the '.thermostatic element, in which case the `arcing `due to breaking `of the circuit would be detrimental to the consistent performance and operation of the latch 'and the thermostatic element, thereby 'to falter the thermal response of the element and the latchin'g action.

Another object of the 'invention is the provision of la thermostatic 'switch in an electrical iitti-ng such 'as a connector plug, by which electrical apparatus is connected to Va 'conventional outlet or power source. If the electrical apparatus has no circuit breaker, it is advantageous to provide a circuit breaker therefor which is subject to being reset and which is connected in the line through which electrical power for the apparatus 4is `obtained. In the disclosed structure, we have provided advantageous larrangement of ia thermostatic element and switch parts with respect to certain members 'of an otherwise conventional fitting, for example, the 'connecting prongs of an electrical plug.

Our invention comprehends .as 4a further obj-ect an arrangement of Ia manually operable resetting member for athermosta'tic switch in an electrical fitti-ng which prevents 'the iitting from being utilized if the resetting `member .is positioned to prevent the switch frorniopenin'g under an electrical overload. W e have arranged the resetting member with respect to the prongs of an electrical plug so that when the resetting member positioned to reset and hold the Aswitch parts together, the prongs .ci the plug are prevented from entering ccnventicnal `prong-receiving .tting Cit er objects and 'advantages :of the invention will yent from the following `description and the :accompanying drawings, `in which :sim-

ilar characters of reference .indicate similar parts throughout the several views.

Referring to the two sheets of drawings:

Fig. 1 is a perspective view of one embodiment of an electrical tting in the ior'mof a :connector plug, in which the thermostatic switch fof our invention is utilized;

Fig. 2 is aplan View of the electrical fitti-ng and thermostatic switch of Fig. l, one part of thefc'asing for the electrical fitting being removed;

Fig. 3 is a transverse sectional View taken substantially on a line 3-3 of Fig. 2, -`andinfthe 'divrection of the arrows;

Fig. 4 is a transverse sectional View taken substantially on a line 4-4 .of Fig. `2, Aand inthe -tlirection of the arrows;

Fig. 5 is a .longitudinal sectional view of our connector plug and thermostatc switch assembly, taken k'substantially on aline `sl-'5 of Fig.. 12,-as indica'ted by accompanying arrows;

Fig. Sis a perspective view of la part o'f fthe illustrated structure;

7 is a fragmentary plan sectional vi'ew yof one end of .the illustrated structure with the parts in one operating position;

Fig. 8 is a fragmentary plan view, 'similar 'to Fig. 2, but showing 'only 'one end of the .structure and depicting difierent operating position'siof certain parts;

Fig. 9 is a plan view, with aparts in section, of a modied vembodiment of our invention having one part or" the casing removed and indicating a 'panel to `which the embodiment is attached;

Fig. .'10 is a irag-mentaray longitudinal `sectional view taken substantially on the line Vl 0-10 of Fig. 9, and Vin 4the direction of the arrows;

Fig. ll .is a transverse sectional view 'taken 'substantially on the line I I-Il .of Fig. A9, and in the direction indicated by arrows; and

Fig. l2 is a fragmentary .plan view, partly in section and similar to Fig. 9, but showing different operating positions Aof parts of the switch.

Having reference to the drawings, in which two Vexemplary embodiments of the invention are shown for illustrative purposes, the numeral '20 designates an insulating casing for one embodiment of a thermostatic circuit breaking device of our invention which takes the form of an electrical plug having two prongs 2l and 22 projecting from one end thereof and connecting cord 23 yextending from the other 'end and including two insulated conductors 24 and 25. r:lhe vcasing 20 comprises two mat-ing parts, one .of which :may be termed :a 'base 26, and the other ya cover 2l. Both the base 2t and the cover 2?! `are made., by molding, of a suitable insulating material ysuch as Bakelite, and .are held together .by athreaded sleeve 28 embedded in the base 26 and a screw 29 passing through the cover 21 and threaded into the sleeve 22. The casing parts and 2'! also form part of the modified embodiment of the invention, as illustrated in Figs. 9 to l2. Certain portions of the casing parts which function the rst embodiment of Figs. 1 to 8 do not function in the second embodiment and thus in some instances stand alone in Figs. 9 to l2 and are more easily seen there.

The prong 2| comprises a long contact portion 39 external to the casing 29, a long connecting portion 3| internal to the casing 2|! and displaced laterally from the external portion 39, and short intermediate connecting portion 32 within the casing. The prong 22 has corresponding contact, connecting and intermediate portions 33, 3 and 35, respectively. The prongs are so disposed on the base 25 that the internal connecting portions 3| and 34 are spaced farther from one another than the external contact portions 30 and 33. The regions of the external portions 30 and 33 of the prongs adjacent the intermediate por- -tions 32 and 35 rest in grooves 35 in an end wall 31 of the base 25; the intermediate portions abut the inner side of the end wall 3T; and the inner ends of the internal connecting portions 3| and 34 extend into recesses 33 and 39 in raised regions 4] and li respectively of the base 26.

A fixed or stationary contact 42 is secured to the inner side of the internal connection portion 34 of the prong 22 near its inner end, and the region of the outer side of the connecting portion 39, directly opposite the contact L32, is backed by a boss i3 of a side wall 44 or the base 26. The side wall, including the boss 153, is below the raised region 4|.

The stationary contact 42 is mounted in posi tion for engagement by .a movable contact 45, as depicted in Fig. 2. The contact 45 is secured to the free end of a spring arm 46 which is genererally in the form of a U having one short leg 47 to which the Contact 45 is secured and a long leg 48, the end of which constitutes a fixed end of the spring arm 45, because it is secured to the base 25 through a metal .terminal 49 and screws 5|. This terminal has a flange 49a to which the fixed end of the arm is joined by a rivet 50. Screws are threaded into the raised region 4| of the base 26 for holding the metal terminal 49 in place on the base. An insulating strip 52 is clamped between the terminal 49 and the raised region 4| and extends in contact with one edge of the connecting portion 34 of the prong to a position somewhat beyond the stationary contact 42, to hold the end of the prong portion 34 in the groove 39. A screw 53 is threaded through the terminal 49 to secure an end of one of the conductors 24 and to the terminal 49. A recess 54 (Fig. 4) in the raised region 4| of the base 25 provides space for the end portion of the screw 53 which is threaded through the terminal 49.

The other of the conductors 24 and 25 has an end connected by a screw 55 to a metal terminal 55 which is secured to the raised region 4i) of the base 26 by screws 5l, as shown in Figs. 2 and 4. An insulating strip 58 is clamped between the raised region 39 and the terminal 55 and extends in contact with the side of the end region of the internal prong connecting portion 3| to hold it in the groove 35. The raised region 49 has a recess similar to the recess 56 on the opposite side of the base, which provides space for the end portion of the screw 55 threaded through the ter- T'QA heat-responsive or thermostaticY element CFI which, in the disclosed structure, constitutes a bimetallic element 59, has a fixed or stationary end secured by fastening means, such as a rivet 99, to a flange 6| of the terminal 55. A latching projection 62 is secured to the free end of the thermostatic element 59. A flexible electrical lead wire or connecting element |53 is metallically bonded, as by soldering or welding, to the thermostatic element at or near its free end, and to the internal connecting portion 3| of the prong 2|.

A latch cam 54, made of a suitable insulating material, is mounted for rotational movement on a spindle portion 55 of a metal stud insert 66 embedded in a raised region 51 of the base 26, as shown in Figs. 2 and 5. The latch cam is supported by a shoulder 55a (Fig. 5) on the insert at the end of the spindle portion S5 and also on a ridge 53 rising from the region 6l of the base 25. The latch cam 3d has a relatively pointed portion 69 disposed for engagement with the free end of the arm 43 to urge the movable contact into engagement with the stationary contact 42. The cam also has a shoulder portion l0 engageable with the latching projection 52 on the thermostatic element. The portions 59 and 1|) are joined by a smoothly curved surface 'H on the latch cam.

The latch cam 64 is moved t0 the position shown in Fig. 2 by a manually operable resetting member 72 which is separately shown in Fig. 6. This resetting member has oppositely extending spindle portions i3 and 'i4 by which it is supported for rotational movement in recesses l5 and i5 in the region 5l of the base 26 and a region il in the cover 2l, respectively. The resetting member i2 has a handle or gripping end portion iii provided with a serrated or ridged end 19 adapted for frictional engagement by a finger of an operator. It also has an operating portion 35 which is connected to the spindle portion 13 and to the handle or gripping end portion 78, and is adapted to engage a curved protrusion 8| on the latch cam 54 when resetting the latch .as indicated in Fig. 8. The ridge 58 on the base 25 is in position to be engaged by the operating portion 3|! of the resetting member, and acts as a stop for limiting movement of the resetting member in one direction beyond the position of Fig. 8, in

which position the handle portion 7B extends from the end of the casing 2|! generally in the direction of the prongs 2| and 22.

When the resetting member l2 is not in use, the handle portion B8 thereof extends transversely of the prongs and lies in ush relationship to the end of the casing 25 between the ends of the 4base 25 and the cover 2, as shown in Figs. l and 2. The serrated end 'iii protrudes from the casing to provide for accessibility of the resetting member. The handle portion i9 has a raised projection 82 on one surface which is fricticnally engageable with cover 2l', as shown in Fig. 3, to prevent the resetting member from being readily swung by gravity from the position of Fig. 2 to that of Fig. 8 when the device is held so that the prongs 2| and 22 extend downwardly from the casing 29.

The cover 27 has a thick portion 83 (Fig. 5) which engages the end of the spindle portion B5 upon which the latch cam 64 is pivoted. There is small amount of clearance between the portion 33 and the latch cam 6 when the latch rests on the shoulder- 56a. Thus the latch is retained on the spindle portion 55, but the thick portion `|33 of the cover does not bind the latch. The thick setting member cannot be employed to defeat the purpose of the thermostatic element.

A second and modiiied embodiment of our invention is illustrated in Figs. 9 to 12. The same base 26 and cover 2'1 comprise the casing. Similarly, the spring arm 46 carries the movable contact 45 at its free end and is shaped generally in the form of a U having the short leg 4? to which the movable contact is secured and a long leg 48 having an end which provides the xed end of the spring arm 46 which is secured to the flange 49a on the terminal 49 by means of the rivet 55. The terminal 49 is secured to the base 2T by screws 5| and carries the connecting screw 53, by which one of a pair of conductors (not shown) is connected to the terminal 49. The other conductor is connected by the screw 55 to the terminal 56, which is secured to the base 25 by the screws 51. The iiXed end of the thermostatic element 59 is secured by the rivet '35 to the flange 6| on the terminal 55. The free end of the thermostatic element 59 carries the projection 52, which is engageable with the shoulder portion 79 on the latch cam 54. The latch cam is mounted for rotational movement on a spindle portion 65 of the insert 65 which is secured in the base 26. The pointed portion 55 or" the latch cam engages the free end of the spring arm 45 to hold the movable contact 45 in engagement with the fixed or stationary contact 42. The exible connector 63 is secured at or near the free end of the thermostatic element 59.

The embodiment of Figs. 9 to l2 differs fro the embodiment of Figs. 1 to 8 in the omission of the projecting prongs and the employment of a connecting bridge 99. The bridge is generally in the form of a wide shallow U having a leg |09, to the inner surface and near the end of which the xed contact 42 is secured, and a leg ll to the outer side of which the exible connector 53 is attached. The bridge has a base |52 provided with an opening |93, which receives a centering or locating projection |543 integrally formed on the base 26. The opening |93 and the projection 94 position the U-shaped bridge 99 so that the stationary contact 42 which is secured thereto is properly positioned for engagement with the movable contact 45 on the spring arm 46. The insulating pieces 52 and 53, which are clamped respectively between the base 26 and the terminal 49 and between the base 26 and the terminal 56, engage respectively the ends of the legs lill and |99 of the bridge to hold the bridge against the base 26 and on the projection |94.

The embodiment of Figs. 9 to 12 is provided with a resetting member |05, which comprises an exterior button portion which, in the disclosed structure, is circular and cylindrical, and has an interior shank |01 having a rectangular section and an actuating projection |63 which depends from the shank |07 and has a rectangular section. The interior shank |91 lits rather loosely between the region 'l1 of the cover 21 and a surface of the latch 64 so as to slide in a groove lilla in the region 1? of the cover 21, as depicted in Fig. 11. The actuating projection |98 is positioned for engagement with the protuberance 8| of the latch cam 64. The casing 29 is secured by screws luga to a bracket |09, which is in turn secured by means such as rivets H9 to a panel I l.` The panel has an opening ||2 through which the button portion |55 of the resetting 4member |95 extends. IThe resetting member has straight-line movement because of the vmounting of the portion |01 thereof in the 8 l groove |0Ia, and so the actuating projection |08 can be moved in a straight line toward and away from the latch cam 64.

In operation of the panel mounting embodiment of our invention just described, one of the two conductors entering the casing 25 through the opening 96 and connected to the terminals 49 and 55 is connected to the electrical device to be protected, and the other of said conductors is connected to a source of electrical power. The other power connection to the device to be regulated is, of course, made directly. Current flows between the device to be regulated and the power source by Way of one line conductor, the terminal 49, the spring arm 46, the contacts 45 and 42, the

bridge 99, the connector 53, the thermostatic element 59, the terminal 55, and the other line conductor. When overload occurs, the thermostatic element 59 heats and exes enough to move the projection 52 on the thermostatio element away from the shouldervportion 79 of the latch 54, and the spring arm 45 moves the movable contact 45 away from the stationary contact 42 and shifts the latch cam 64 about the spindle portion 65 until the curved surface H on the latch cam is opposite the projection 52. Separation of the contacts 42 and 55 breaks the circuit, and the thermostatic element then cools and returns to its original and normal position, with the projection 52 disposed for engagement with the latch cam 54. Before the device to be regulated can again be operated, the latch 5t must be reset. This is accomplished by shifting of the resetting member |95 linearly into the casing from the position shown in Figs. 9 and 10 so as to make the projection |99 on the resettin0r member engage the protuberance 5| and effect rotational movement of the latch cam. Incidentally, the position of the button portion |95 of the resetting member |95 may be employed to indicate the condition of the thermostatic device of Figs. 9 to 12. If the button portion is in, that is, protrudes only a small amount from the panel i I then the latch cam 55 must be in the resetting position and the contacts 45 and 42 in engagement with one another. When overload has suiiciently heated the thermostatic element 59 to move it away from the latch cam 54, thereby permitting the latch cam to be angu- I larly shifted to the position of Fig. 12 by the spring action of the spring arm 45, the latch cam will push the resetting member 95 so that the button portion thereof protrudes the maximum amount. Like the embodiment of Figs. l to 8, the embodiment of Figs. 9 to 12 has the thermostatic element 59 and the spring arm arranged in generally parallel side-by-side relation, the shoulder portion 19 and the pointed portion 69 of the latch cam 64 displaced from one another about degrees, and the spindle portion E5 about which the latch cam 54. rotates generally aligned with the spring arm 45. The result of this arrangement is that the embodiment of Figs. 9 to 12 has the advantage of compaotness that permits the embodiment to be arranged in an electrical fitting of about conventional width, such as illustrated by the casing v26|.

While we have illustrated a preferred embodiment of our invention, many modifications may be made without departing from the spirit of the invention, and we do not wish to be limited to the precise details of construction set forth, but desire to avail ourselves of all changes within the scope of the appended claims.

Having thus described our invention'what we having a latching projection- .at the? other end, a stationary Contactl supported in`I anxed position' relative to the ca-singg a movable' contact,r a resilient arm carry-ing the Inova-ble Contact at one end thereof and at a posit-ionY aiignedf for'- engagement with the stationary contact,- meanssup:4 porting the other end' of the armA` at a fined posi-- tion relative tothe casing and5 so that the normalresilience of the armA tends to li'eep the movabler contact out of engagement with theA stationary contact, the arm extending generally" iir saidA one direction from one endl to the' other, and a latch element mounted for rotational movement rela-- tive to the casing and having a contact actuatin'g portion engage'able with the arm' and aV latch porticnl displaced angularl'y and: linearlyv from the contact actuating portion, said latchl portion of the latch eiementbeing releasea'bly engageable with the latching projectionv on the therm'ostatic element to hold the contact actuating portion against the arm so asv to-hcld the movable contact in engagement with the stationary contact.

2; A thermostatie switch comprising an insulating' casing, a thermostatic element nxed in positionat one endrela-tive to the casing and extending in one direction from said one end and having a latching projection at the other end, a stationary contact support-'ed in a fixed position relative to the casing; aI movableV contact, a resilientarm carrying the movable contact at one end'v thereof and at a position" aligned for engagement with thestationarycontact, meanssupporting the other end of the armV at al i'xed position relative to the casing and so that theinormal resilience of the arm tendsto keep" the' movable contact out of engagement with the'- stationary contact, the arm extending generally said one direction from one end to' theothei, and a latch element mounted for rotational` movement rela-- tive to the casing andl having" a contactact'uating portion engagea'blejwith thearm and e; latch portionA displacedangularlyan'd linearly from the contact actuating portion, said latchportion` of the latch element being engageable'with theproje'ction on thethermostatic element to holdl the* contact actuating portion against the arm' so as toholdl the movable contact in engagement with'v thest'ationary contact, the1 arm being generally U-shaped andY having a short leg carrying the movable contact and a long leg supported rela'- 'tive' to the insulating casing bysaid means, and

the said Contact actuatingv and latch portions of one direction from its fixed: end to its freef end;

inea-ns electrically connecting the freel end of the thermostatic elementr andoneprong, a: 'xed contact secured to-the otherprongf, a spring arm having one end xed to the casing and the other end free, said spring arm being provided with a movablecontact engagea'ble with the nxed' contact andi extending. generally in saidV one direction from its'xedl end to its free end in side-byside relationshipv with' the thermostatic element', the resilience' of the' springV arm being such that it normally biases thefm'ovable contact away fromv the fixed Contact, and ar latch' element mounted for rotational movement on the casing and having angularly spacedv portionsv engageable with the projection o'n the thermostatic element and thefree" end of the spring arm, whereby engagement ofthel projection on the thermostatic element withione of said portions of the latch elementI holds the latch element in a position such that the' other portion thereof acts against the spr-ing arm to hold the movable contact against the'. ine'd contact, andi. when the thermostatlc element heats sufciently to shift the projection away' from the latchelement the latch element noilonger holds the spring arm and the movable contact moves away from the-fixed contact.

4. A plug connector type oi thermostatic switch as specied in claim 3, and further comprising a reset member mounted for swinging movement relative to the casing and having a portion inter-nali to the casing and engageable with the latch element, said reset member also having a portion external to the casing and exposed for manual manipulation, the reset member being swingable between a retracted position in which the external portion isL transverse of the prongsand the internal portion is free ofV the latch and a` projecting position inwhich the external portion extends-between and generally in the direction of the externalv portions of the prongs andl in which the internal portion effects movement of the latch element to a position such that the projection on the thermostatic element engages said one of the portions of the latch element to hold theV movable Contact engagement with the xed contact.

5. A plug connector type of thermostatic switch as specied in claim 4, and further comprising terminals securing the fixed ends of the bimetallicelement and the' spring arm to the casing adjacent the end-thereof away from the end from which the prongs project, said casing having an opening therein adjacent the terminals for receiving conductors connectable with the terminals.

6l A plug connector type of themostatic switch asspecified in claim 35 and whereinl the outer endof each prong is offset from the portion thereof which is insideV of the casing, the interior portions being spaced farther apart than the exterior portions, andthe thermostatic element andthe spring' arm being positioned between the interior' port-ions ofthe prongs.

7. A- plug connector type of thermostatic switch as' specified in claim 3, and further comprising terminals securing the fixed ends of the thermostatic element'andI the'spring arm to the casing adjacen'tthe end' thereof away from the end from which the prongs extend' outsidev of the casing', said'l end of? the casing adjacent the terminals having" an opening therein for receiving conductors connect'ablewith the terminals, and the combination furtherv comprising insulating pieces clamped between the' terminals and the casing and engaging the prongs to hold them in' the casing.

8. A thermostatic switch comprising anI insulating casing, a thermostatic element having a x'edend-mounted on-the casing and a :free end, said" the'rmos'tatic: element extending inr substantially a predetermined direction from its xed end to its free end and having a projection near its free end, a movable arm having a fixed end mounted on the casing and a free end provided with a movable contact and extending generally in the said predetermined direction in side-byside relationship to the thermostatic element, and a bridge extending across the thermostatic element and the arm is spaced relation thereto, a xed contact secured to one end of the bridge at a position for engagement with the movable contact, a connector providing an electrical connection between the other end of the bridge and the free end of the thermostatic element, and a latch element mounted for rotational movement on the casing and having angularly displaced portions engageable with the free end of the arm and the projection on the thermostatic element for holding the contacts in engagement.

j 9. A thermostatic switch as specied in claim S, and wherein the bridge is generally in the form of a U, the stationary contact is secured to one leg of the U, the Said connector is joined to the other leg of the U, and the said portions of the latch element are angularly displaced from one another approximately ninety degrees.

10. A thermostatic switch as specified in claim 9, wherein the latch element is located near one end of the casing, and the combination further comprises a manually movable resetting member projecting through said one end of the casing so as to be engageable with the latch element to eiect movement of the same to a position in engagement with the arm and the projection on the thermostatic element, and terminals mounting the fixed ends of the thermostatic element and the arm near the other end of the casing, the said other end of the casing having an opening therein for receiving conductors connectable with the terminals.

11. A thermostatic switch as specified in claim 10, and further comprising insulating pieces clamped between the terminals and the casing and engaging the ends of the legs of the U-shaped bridge to hold it in place in the casing.

12. A thermostatic switch as specified in claim 11, and wherein the base of the U-shaped bridge has an opening therein, and the casing has a projection engaging the opening to locate the bridge properly in the casing.

13. A thermostatic switch comprising an insulating casing, a pair of prongs projecting from one end of the casing in xed relationship to one another, a stationary contact mounted on one prong inside the casing, a movable contact shiftable toward and away from the stationary contact for engagement therewith, a thermostatic element electrically connected to the other prong inside the casing, means comprising a movable part interposed between the movable contact and the thermostatic element for effecting disengagement of the movable contact from the stationary contact in response to predetermined heating of the thermostatic element, and a resetting member mounted in the casing and movable to a resetting position in which it actuates said movable part in a manner to effect reengagement of the contacts, and in which position the resetting member projects from the said one end of the casing adjacent the prongs, the resetting member being of a size to prevent insertion of the prongs in an electrical fitting when it projects adjacent the prongs.

14. A thermostatic switch as specified in claim 13, and wherein the resetting member is mounted in the said one end of the casing for swinging movement so as to move between the said resetting position in which it extends out from the said one end of the casing in the direction of projection of the prongs and an inoperative position in which it extends along the said one end of the casing and beyond the side thereof so as to be readily engageable for manual movement to the resetting position.

15. A thermostatic switch comprising an insulating casing comprising a base and a cover, a pair of prongs projecting from the casing, a stationary contact associated with one prong inside the casing, a movable contact positionable for engagement with the stationary contact, a thermostatic element mounted on the base, means enabling the thermostatic element when heated to take the movable contact away from the stationary contact, the base having an opening leading from its outer side to the thermostatic element and a recess in the outside of the base at the opening, and an adjusting element mounted in the opening so as to engage the thermostatic element, one edge of the cap having a tongue tting in the recess in the base so as to cover the opening at the outside of the base.

1o. A thermostatic switch comprising an insulating casing, a thermostatic element xed in position at one end of the casing and extending freely along one side of the casing toward the other end thereof, said thermostatic element having a latching projection near its free end which extends away from said one side of the casing, a stationary contact supported in a fixed position relative to the casing on the side opposite the thermostatic element, a resilient arm carrying a movable contact near one end thereof at a position aligned for engagement with the stationary contact, the other end of said resilient arm being fixed in position relative to the casing at a position opposed to the xed end of the thermostatic element, said resilient arm extending freely along the side of the casing opposite the thermostatic element and normally to biasing the movable contact away from the stationary contact, a latch element mounted in the casing between the resilient arm and thermostatic element, said latch element having a latch portion and a contact actuating portion separated thereon and disposed respectively for releaseable engagement with said latching projection on the thermostatic element and said resilient arm for retaining the contacts in engagement, and a manually operable member movably mounted on the casing for effecting movement of the latch element to its contact holding position.

17. A thermostatic switch as defined in claim 16, and further characterized by an adjustable element movable to adjusted positions relative to the casing and engaging the thermostatic element to effect adjustment of the temperature at which the latch portion of the latching element is disengaged by the latching projection of the thermostatic element.

RAY J. D. ROBERTS. ALFRED H. FAULKNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,399,406 Toth Apr. 30, 1946 2,427,390 Dear Sept. 16, 1947 2,508,637 Bolesky May 23, 1950 

